Sheet metal forming has been used in the industry for years for creating metal parts from a blank sheet metal, for example, automobile manufacturers and their suppliers produce many parts using sheet metal forming.
One of the most used sheet metal forming processes is deep drawing, which involves a hydraulic, mechanical or servo press pushing a specially-shaped punch into a matching die (i.e., part of a tool set) with a piece of blank sheet metal (i.e., work-piece) in between. Example products made from this process include, but are not limited to, car hood, fender, door, automotive fuel tank, kitchen sink, aluminum can, etc.
Product surface contains the desired pattern/shape of a sheet metal part at the end of the deep drawing process. During the deep drawing operation, binder is used for holding the work-piece. After the work-piece is shaped by the tool set (i.e., punch and matching die), unwanted portion of the work-piece is cut out along the trim lines if required. Any trim line located along the periphery of the product surface becomes boundary line. At this point, the work-piece experiences a phenomena or effect referred to as springback to a permanently deformed geometry. The springback effect includes physical phenomena of the elastic deformation being released while the plastic deformation stays. In order to produce a part properly and economically to a desired geometry, it is critical to design a tool set in a configuration that a part can be produced without further modifications.
To achieve the compensation of springback, overbending of the sheet metal work-piece is generally required. Prior art approaches has been a trial-and-error method of modifying the physical die. With the computer aided engineering, numerical simulations of this trial-and-error approach have been used. However, there are problems in automated numerical simulation of iteratively modifying a tool set. For example, in certain situation, convergence cannot be obtained in a numerical simulation due to errors in a computer generated model of the tool set particularly along the boundary line. It would therefore be desirable to have improved methods of designing geometry of a tool set in a numerical simulation of sheet metal forming operations including effects of springback compensation.